Brad, Rich,
The original intent of my message was to make sure we
were making explicit statements rather than implicit
ones. Simply stating that .3x flow control only works
over point-to-point links doesn't really capture the
issue.
After more thought and reading your comments, I tend
to agree with you both, that .3x flow control was not
intended for links such as the multiple sections and
lines of a WAN link and should not be supported. I
would like to see this explicitly stated in the draft.
If you have suggestions where this should be done,
either submit a comment yourself or send me them and
I'll submit one. I plan to take another look at the
document and propose some wording to make this
statement.
Regards,
Ben
Rich Taborek wrote:
>
> Ben, Brad,
>
> We're about 5 or 6 tangents off the old main thread by now, so I started
> a new one. I'd like to take this opportunity to clear something up about
> 802.3 point-to-point links, including those being specified in IEEE
> P802.3ae. At least I'd like to see some discussion on this topic :-)
> Section, Line and Path are not relevant for any P802.3ae links, whether
> they be LAN or WAN links. There is quite a bit of "bleeding" of
> management information for SONET Section, Line and Path into the WIS. I
> assume that the reasoning for this is to support the management of this
> SONET/SDH specific information in a "standard" manner.
>
> What I don't see in the current draft is any description of or any
> requirement for the distinction of Section, Line, or Path. The link
> between two P802.3ae PMDs, whether they be two LAN or WAN PMDs is simply
> a point-to-point link. Section, Line and Path are only relevant in
> SONET/SDH equipment to which a WAN PHY may be attached. In the case that
> the SONET/SDH equipment and its associated Sections and Lines and Paths
> bisect two WAN PHYs, we have two point-to-point links and a SONET/SDH
> cloud in between. I don't believe that 802.3x flow was designed for the
> latter configuration.
>
> I agree with Brad's wording: "Flow control is also only for
> point-to-point links". I don't believe that either 802.3 flow control or
> point-to-point links are applicable to or representative of "WAN links".
> Note that "WAN link" is usually typically synonymous with SONET/SDH WAN
> links rather than IEEE 802.2 WAN links, whether based on LAN or WAN PHY
> links.
>
> We certainly have a terminology problem. WAN flow control is an issue
> which is beyond the scope of 802.3 and simple 802.3x point-to-point flow
> control.
>
> Happy Holidays,
> Rich
>
> --
>
> Ben Brown wrote:
> >
> > Brad,
> >
> > I just wanted to pick up on something you wrote:
> >
> > "Booth, Bradley" wrote:
> > >
> > > Flow control is also only for point-to-point links.
> > >
> >
> > I hope you aren't implying that a WAN link with multiple
> > lines & sections (do I have the nomenclature correct?) is
> > not a point-to-point link. From an ethernet MAC perspective,
> > these are just as point-to-point as a 3 meter jumper.
> >
> > I can't even begin to imagine the amount of buffering
> > required to run .3x flow control over such a link. I would
> > be interested in a short note from someone with experience
> > regarding what kind of potential latencies such a link
> > might have.
> >
> > Thanks,
> > Ben
> >
> > "Booth, Bradley" wrote:
> > >
> > > Time to hit the RESET button on this one. :-)
> > >
> > > First, you are correct in the assumption that a 40km link buffer requirement
> > > (1MB, not Mbit) will greatly exceed the internal latency.
> > >
> > > Not everyone in the world will design equipment to work up to 40km. Some
> > > will create equipment that works up to 65m, and to optimize that equipment,
> > > they're not going to want to have 1MB of buffering just for flow control
> > > (that would be overkill). In these short distance applications, knowing the
> > > maximum latency in the link partner device and in the local device will
> > > permit designers to optimize their flow control buffering.
> > >
> > > Flow control is also only for point-to-point links.
> > >
> > > Happy holidays,
> > > Brad
> > >
> > > -----Original Message-----
> > > From: Roy Bynum [mailto:rabynum@xxxxxxxxxxxxxx]
> > > Sent: Friday, December 22, 2000 10:31 AM
> > > To: Manish D. Agrawal; Boaz Shahar; Manish D. Agrawal;
> > > THALER,PAT (A-Roseville,ex1); HSSG
> > > Subject: RE: delay constraints from XGMII to XAUI
> > >
> > > Manish,
> > >
> > > One of the issue of the delay is that there are other
> > > distances
> > > involved. The 850nm 65m PHY will not have the same
> > > transmission media
> > > latency as the 1500nm 40km PHY. Add latency due to long
> > > haul optical
> > > services for the WAN PHY and you have got even more issues
> > > with flow
> > > control response latency. These are going to be issues of
> > > discussion as we
> > > go forward.
> > >
> > > Thank you,
> > > Roy Bynum
> > >
> > > At 11:32 AM 12/22/00 +0530, Manish D. Agrawal wrote:
> > > >Hello Boaz,
> > > >
> > > >As you said "The only MAC requirement I can think of for
> > > bounding the
> > > >lower layer delay is for buffer sizing for 802.3x flow
> > > control. That has
> > > >been the factor for keeping the delay tables in various
> > > clauses. "
> > > >
> > > >But, since the delay for the flow control seems to be
> > > greater than 1 Mbit,
> > > >why there are delay constraints of 256/212/272 bits in
> > > various clauses,
> > > >which are negligible as compared to the delay of 40KM
> > > fiber?
> > > >
> > > >Correct me if I am wrong.
> > > >
> > > >Best Regards,
> > > >Manish
> >
> > -----------------------------------------
> > Benjamin Brown
> > AMCC
> > 2 Commerce Park West
> > Suite 104
> > Bedford NH 03110
> > 603-641-9837 - Work
> > 603-491-0296 - Cell
> > 603-626-7455 - Fax
> > 603-798-4115 - Home Office
> > bbrown@xxxxxxxx
> > -----------------------------------------
>
> -------------------------------------------------------
> Richard Taborek Sr. Phone: 408-845-6102
> Chief Technology Officer Cell: 408-832-3957
> nSerial Corporation Fax: 408-845-6114
> 2500-5 Augustine Dr. mailto:rtaborek@xxxxxxxxxxx
> Santa Clara, CA 95054 http://www.nSerial.com
--
-----------------------------------------
Benjamin Brown
AMCC
2 Commerce Park West
Suite 104
Bedford NH 03110
603-641-9837 - Work
603-491-0296 - Cell
603-626-7455 - Fax
603-798-4115 - Home Office
bbrown@xxxxxxxx
-----------------------------------------